Metallocene Catalyst and Method for Producing an Olefin Type Polymer
An olefin polymerization catalyst comprising a metallocene compound having two ligands having cyclopentadienyl ring structures, and a cocatalyst (a methylalumoxane or a boron compound), has been widely used as a catalyst for producing a polyolefin. Particularly, a polymerization catalyst comprising a metallocene compound having a structure wherein two ligands are bridged by carbon or silicon, is known as a catalyst for producing LLDPE or an isotactic or syndiotactic polypropylene.
However, with respect to a metallocene compound (catalyst) wherein the bridging structure is boron, little has been reported, and only complexes having cyclopentadienyl groups and indenyl groups, are known (WO97/15581, Organometallics 1999, 18, 2288, J. Organomet. chem. 1997, 536-537, 361). In the case of these complexes, the activities for the production of LLDPE (linear low density polyethylene) or for the production of a polypropylene, are not so high.
Method for Producing an Aromatic Vinyl Compound-Olefin Copolymer
Some styrene-ethylene copolymers obtainable by using so-called single-site catalyst systems comprising a transition metal compound and an organoaluminum compound, and methods for their production, have been known.
JP-A-3-163088 and JP-A-7-53618 disclose styrene-ethylene copolymers where no normal styrene chain is present i.e. so-called pseudo random copolymers, obtained by using a complex having a so-called constrained geometrical structure. Here, a normal styrene chain is meant for a head-to-tail bond chain. Further, hereinafter styrene may sometimes be represented by St.
However, phenyl groups in the alternating structure of styrene-ethylene present in such pseudo random copolymers, have no stereoregularity. Further, no normal styrene chain is present, whereby the content of styrene can not exceed 50 mol %. Further, the catalytic activities are practically inadequate.
JP-A-6-49132 and Polymer Preprints, Japan, 42, 2292 (1993) disclose methods for producing similar styrene-ethylene copolymers wherein no normal St chain is present, i.e. so-called pseudo random copolymers, by using a catalyst comprising a bridged metallocene type Zr complex and a cocatalyst.
However, according to Polymer Preprints, Japan, 42, 2292 (1993), phenyl groups in the alternating structure of styrene-ethylene present in such pseudo random copolymers, have no substantial stereoregularity. Further, like in the case of a complex having a constrained geometrical structure, no normal styrene chain is present, and the styrene content can not exceed 50 mol %. The catalytic activities are also practically inadequate.
Further, it has recently been reported to produce a styrene-ethylene copolymer close to an alternating copolymer having a stereoregularity under a condition of an extremely low temperature (−25° C.) by using a specific bridged bisindenyl type Zr complex, i.e. rac[ethylenebis(indenyl)zirconium dichloride] (Macromol. Chem., Rapid Commun., 17, 745 (1996)).
However, from the 13C-NMR spectrum disclosed, it is evident that this copolymer has no normal styrene chain. Further, it copolymerization is carried out at a polymerization temperature of at least room temperature by using this complex, only a copolymer having a low styrene content and a low molecular weight is obtainable.
JP-A-9-309925 discloses a method for producing a styrene-ethylene copolymer employing a bridged zirconocene type catalyst having unsubstituted indenyl groups or substituted indenyl groups, wherein a boron bridging group having a substituent is disclosed. However, no specific disclosure is given relating to a specific boron-bridging complex. Further, JP-A-11-130808 discloses a method for producing a styrene-ethylene copolymer employing a bridged zirconocene type catalyst having benzindenyl type ligands, but there is no disclosure relating to a boron-bridging group.
The present invention is intended to provide a metal catalyst component for polymerization, and a method for producing an olefin (co)polymer and a method for producing an aromatic vinyl compound-olefin copolymer, by means thereof.
Hereinafter, an aromatic vinyl compound-olefin copolymer (styrene-ethylene copolymer) may be sometimes referred to as an olefin-aromatic vinyl compound copolymer (ethylene-styrene-copolymer).